Black is dead in the lower left corner, because black has no move to finish the ko. So white can leisurely respond to every threat until black has nothing more to try. There are situations in which neither player can kill the other (Seki).

It seems the demo board is private, hence invisible for us… But now that you have made an sgf, it should be easy to download the private game and either upload it to a demo board that is public, or post it here on the forum

You could easily have saved the upper right stones, while keeping the initiative (see variation).

General comment: you tend to play too close to white and that results in weak stones. Unfortunately the app seems to be weak so it doesn’t punish you. For example A11 is too small and white should not respond directly (see variation). Try to keep in mind the big picture and play large moves, just like you did with the very good moves at K4 and Q10.